Production of oxy compounds of tantalum and columbium from the ores



Patented Apr. 21, 1931 i I uureosrAres PATENT OFF C com o. FIN'K AND LESLIE G, ammnss' or NEW-3mm; imam, Assrenons ron'rriznav V METALCORPORATION, or new YORK, any, A conronarron or DELAWARE .PRoDUc'rroN or oxY comroulvns'or TANTALIiM AND coLUtInIU a IEROM- THE ORES No Drawing.

' Our invention relates to methods of. recovering tantalum and' columbium from the ores, and more particularly to processes for the leaching of tantalum and columbium ores.

- The two metals, tantalum and columbium are closely associated in nature and practically all tantalum and columbium ores con tain bothtantalum and columbium minerals. Various methodsof recovering these metals 7 10 from the ores have been proposed in the past.

Von'Bolton, for instance, fused the ore with soda ash or other alkali metal salts and leached the-fusion; By this method he obtained the compounds sodium tantalate and P115 sodiumcolumbate but the process is very.

complicatedand expensive. 1 We have found that both hydrofluoric and oxalic acids have leaching properties in respect of these ores but that, when used singly they are relatively very weak. Hydrofiuoric acid, however, has

much stronger leaching properties than oxalic acid.

'Wehave discovered, however, that an acid capable of decomposing tantalum" or ..columbium ores such as hydrofluoric acid combined withan organiciacid in which tantalum and columbium will dissolve, such as: oxalic, tartaric, succinic or citric acids'forms a very effective leaching reagent fortantalum and I 730 columbium ores and particularly so when conducted at a temperature of "about the condensation point ofsteam. Similarly calcium fluoride and sulphuric acid in'the-presence of these organic acidsmay. be used and whilev "3 they act more slowly than the hydrofluoric solution. The solution, therefore,.rremains more concentrated in free hydrofluoric acid centration of free hydrofluoric acid at any time; which is an important factor in the m extent ofthe'1each.-

is in equilibrium and moves to theright saturation point in a solution of hydro- Application filed May 20, 1926. Serial No."110,473.

In the case of the, calcium fluoride and sulphur c acid; combination the reaction the consumption of hydrofluoric acid in re, action and volatilization. ,But owing to the formationof oxalic acid compounds of the tantalum and columbium, there will be less of j the hydrofluoric acid consumed in the reaction and, consequently, hydrofluoric acid will be less rapidly generated by the action of the sulphuric-acid uponthe calcium fluoride. Theefl'ect of. this combination is, therefore,- slower than where hydrofluoric acid is directlyused. I V 2 We have found experimentally that a com bination of hydrofluoric acid with oxalic acid causes a much greater yield than the summation of the yields of both acids used singly. For example, from;l00 grams of the ore, leaching with these two acids singly and then in combination, the quantities of reagent used ineach .instance being. equivalent, we obtain the following results:

w 7V Grams Ox'alic acid alone f .16 Hydrofluoric acid alone; .30 Combination ofoxalic and hydrofluoric 32CldS i 111 applying our invention we use at the a beginning, for each 100parts of finely ground ore 100 parts of aleachingsolution containing for good f resultsoxalic acid dissolved to the 5 fluoric acid; Heating to about to 98 C.

- hastens the-action of the leach. ASexceptionallygood resultsmay be obtained by introducing steam directly into the solution and there condensing it, it is apparent thatthe above proportions will not hold good over a 'long-periodof steam condensation. It is also to be noted that-the quantity of hydrofluoric acid mentioned is equivalent to the hydrofluoric acid available fromlOO parts of cal- 95 a V 'cium fluoride. available to react upon the ore. :It 1s the con- Itis believed that the oxalic acid acts as a solution link for .thetantalum and columbium oxides 'andthat, its function is not that 'ofa mere"so1vent.; The compounds resulting from this leach a parently require free oxalic acid to hold t iem in solution, and as the concentration of free oxalic acid decreases, actual precipitation of the oxides from the solution occurs. An apparent break of the solution link takes place.

The leaching solution, of course, takes up not only tantalum and columbium but alsoinon,titanium, manganese and other impurities that may present. Tin in the form of $110 is, however, not attacked by the acids and: remains behindwith the gangue. The solution becomes quite thick and syrupy but upon precipitation with ammonium hydroxide (NH,OH)' or other alkali the tantalum and columbium are precipitated but the iron, titanium, manganese and other impurities remain in the solution and are not precipitated.

its above pointed out, the decomposing properties of the hydrofluoric acid make it a very im ortant factor inthe extent of the leach. here should, therefore, be as much oxalic acid present as the solution will hold in order that the valuable constituents of the are; in thiscase tlie'tantal'um and columbium, may be'takenup-insolution to the fullest entent. When the quantity of oxalic acid is substantially reduced, there is a very marked fiilfing'ofi in the ield. I

It is believed t at a large number of adsorl'aed carboxylic groups are necessary to Hold the tantalum and columbium oxides in,

solution and that oxalic acid furnishes more (If these" groups'with less additional weight to the molecule than any other carboxylic acid, while the group also will be directly attached to the molecule and not through a carbon chain. Succinic, tartaric and citric acids having a more complicated structure, all exhibit this property but to a less degree than oxalic acid. It may be' also that more ad sorbed groups may be necessary to holdjthe tantalum oxide in solution than in the case of the lighter columbium oxide.

It will beevid'ent, furthermore, that sevnnadl steps in the process which are hereinabove described as being simultaneous may hepursued separately. It is possible for instance to decomposev the ores by subjecting .themto the action of hydrofluoric acid as one step and then to dissolve the tantalum and eolumbiumout of the decomposed ore by oxalic acid'asa separate step.

"Having: thus described our invention what we claim. is:

1.. A leaching solution for tantalum and columbium orescomprising hydrofluoric acid andoxaliik: acid.

2. A leaching solution" for tantalum and columbium ores comprising calcium fluoride anal1 sulphuric acid in the presence of oxalic 8% t i i v 3. A leaching solution for tantalum and columbium ores comprising a combinationof compounds adapted to generate hydrofluoric acid, and a carboxylic acid. 7

4. A leaching solution for tantalum and columbium ores comprising an acid adapted to decompose said ores and a carboxylic acid.

5. The process of producing oxy'compounds of tantalum and columbium from the oreswhich comprises the leaching of said ores with a solution containing free hydrofluoric acid and free oxalic acid.

7. The process of producing 'oxy compounds of tantalum-and columbiumv frourthe ores which comprises subjecting said ores to the action ofhydrofluoric acid in the presence of a carboxylic acid.

7. The process v of producing oxy compounds of tantalum andcolumbium from the ores which comprises subjectin -said ores to the action of hydrofluoric aci in the pres ence of a carboxylic acid.

8. The process of producing oxy compounds of tantalum and columbium; from the ores which comprisessubjecting said ores to the action of calcium fluoride and sulphuric acid; in aqueous solution in the presence of a carboxylic acid.

9. The process of producing oxy compounds of tantalum and columbium from the ores which comprises decomposing said ores.

by means ofhydrofluoric acid and holding in solution the metal compoundsresulting from decomposition by means ofa carboxylic acid.

10. A process for the production of any compounds-of tantalum and columbiumfrom the ores which comprises the leaching of said ores with a solution containing hydrofluoric acid and a carboxylic acid while maintaining said solution at a temperature substantially equivalent to that of thecondensation temperature of steam;

11-. A process for the production of any compounds of tantalum and columbiumfrom the-ores which comprises the leaching of said ores with a solution containing-hydrofluoric acid and a carboxylic acid while simultaneously condensing. steam in the solution.

12. A process for the production; of any compounds of tantalum andscolumbium from the ores which comprises the leaching of said oreswith a solution containing, com ounds adapted to generate hydrofluoric acid and a carboxylic acid while simultaneously condensing steam in the solution.

13. A process for the production ofoxy compounds of tantalum and columbi llm comprising the leaching oftantalum and'columbium ores with a soliitioncontaining hydrofluoricacid and a carboxylic acid, followed by the precipitation out of the solution cfthe tantalum and columbium oxy compounds the addition of an alkali thereby effecting a separation from iron and other constituents of said ores; 5; 7

14. A process for the production of oxy compounds of tantalum and columbium 001m prising the leaching of tantalum and columbium ores with a solution containin hydrofluoric acid and a carboxylic acid, ollowed by the precipitation out of the solution of the tantalum and .columbium oxy compounds by the addition of ammonium hydroxide.

15. A process for the production of oxy i compounds of tantalum and columbium comfluoric acid and a carboxylic acid, while si-,

prising the leaching of tantalum and columbium ores with a solution containing hydromultaneously condensing steam in said solution, and subsequently precipitating the tantalum and columbium oxy compounds out of 7 the solution by the addition of ammonium hydroxide.

16. A leaching solution for tantalum and columbium ores consisting of oxalic acid dissolved to the saturation point in a 50% hydrofluoric acid solution. a

In Witness whereof, we have subscribed our names hereto this 15th day of May,

COLIN G. FINK. LESLIE G. JENNESS. 

